SUBGRIDDED FDTD SIMULATION OF ELECTROMAGNETIC FIELDS IN INHOMOGENEOUS EARTH MEDIA FOR GEOPHYSICAL PROBING APPLICATIONS

Abstract

We describe a finite-difference time-domain(FDTD) algorithm to simulate propaga-tion/diffusion of electromagnetic fields in inhomogeneous earth media. The algorithm employs a cylindrical grid to conform to usual measurement apparatus geometries of well logging tools for oil and gas exploration. The grid is made very compact around the measurement apparatus by using a cylindrical perfectly matched layer (PML). In order to avoid the disparate cell sizes inherent to a cylindrical grid, a subgridding al-gorithm is employed in the radial coordinate. This FDTD scheme is validated against numerical mode matching (NMM) results and used to simulate logging tools in com-plex geophysical environments